[EM] Realistic strategy questions

[Toby Pereira]

Can I ask which voting systems will be included in this? Among other things 
I'd like to see how different Condorcet methods compare with each other and 
also margins v winning votes. Certainly something to look forward to, 
although I have nothing useful to add about the strategy types at the 
moment.
 

On Monday, 24 February 2014 17:46:39 UTC, Jameson Quinn wrote:

> I have been working on my program for measuring the Voter Satisfaction 
> Efficiency (formerly known as BR) of various systems. It's just about ready 
> to do a big run, but before I do that, I'd like to get as many of the 
> activists here to say what they think are reasonable settings for 
> generating scenarios. In particular, I have to decide proportions for 
> various kinds of strategic voters.
>
> Here's a few possible kinds of voters:
>
>    1. Honest: Will always map their utility onto a vote as honestly 
>    (linearly) as possible, after normalization over the range of candidates 
>    available.
>    2. Media-based Honest: As above, but when normalizing, they will 
>    ignore all candidates who are worse than both polled frontrunners.
>    3. Fully strategic: Will always strategize by maximizing the ballot 
>    distance between the two (honestly) polled frontrunners. 
>    4. Weakly strategic: Will strategize, but only as much as "necessary". 
>    That is, assuming no other voters strategize, they will shift their vote, 
>    focusing on the margin between the polled winner and runner-up. In a 
>    Condorcet system, such a voter would always be honest. In a median system, 
>    they would exaggerate to ensure they graded the winner and runner up on 
>    opposite sides of both of their polled total grades, but not necessarily to 
>    an extreme; so if their honest vote was A,B,C,D,F and the polled grades 
>    were D,C+,C-,D,D, then they'd vote A,B,D,D,F.
>    5. Lazily strategic: Fully strategic if and only if their weakly 
>    strategic vote would not be identical to their honest vote.
>    6. Threshold strategic: Fully strategic if and only if their utility 
>    (satisfaction) difference between the polled frontrunners is greater than 
>    some threshold (in absolute value)
>    7. One-sided strategic: Will strategize if and only if they prefer the 
>    polled runner-up to the polled winner.
>    8. 20/20 hindsight: Fully strategic if and only if one of the last N 
>    election results was changed by strategy. (When simulating, you'd just use 
>    some constant probability for each election system, and find an equilibrium 
>    point for that probability). 
>    9. Sheep: strategic iff more than X% of the non-sheep voters are.
>    10. Cliquish: Certain probability of being each of the above kinds, 
>    except with a certain extra probability of being the same as other voters 
>    who share similar utilities. 
>
> Obviously, it would be easy to extend the above list by combining the 
> various aspects there.
>
> Personally, I find ALL of the above strategic types to be essentially 
> plausible. I know that the full decision rule for some (such as weakly and 
> lazily) are more complex than the explicit thought processes of 99.99% of 
> voters, but in practice I think it would be easy to end up acting like that 
> through implicit and/or subconscious heuristics. Thus, in particular, I 
> find it extremely IMplausible that the electorate would consist only of 
> types 1 and 3, as previous BR simulations generally assumed.
>
> The question, then, is: how many of each kind of voter should I put in? Of 
> course, I'll run several scenarios, but there's no way I can fully explore 
> the 8-simplex of possible combinations of the above 9 voter types. So I 
> have to choose where to focus my attention.
>
> And furthermore, I think it's valuable to say which percentages you find 
> plausible before you learn how your favorite voting system does under those 
> percentages. In my debugging so far, I've gotten a glimpse of the impact of 
> types 1, 3, 4, 5, and 7 above; but I have not looked at the rest at all. So 
> here's a scenario I find reasonable, and which I really don't know how it 
> will turn out for my currently-favorite systems:
>
> Each voter has a "honesty type" which are 50% honest and 50% media-based; 
> a "strategy type" which are 75% full and 25% weak; and a "decision type" 
> which are 30% hindsight (N=1-3), 30% threshold (X=0.5-2 SD), 20% lazy, 10% 
> one-sided, 5% always-honest, and 5% always-strategic. They use their 
> "decision type" to decide whether to vote according to their "honest type" 
> or their "strategic type". Cliquishness is around 70% (note that even at 
> that high level, there are good chances of a scenario where the 
> cliquishness does not lead to one-sidedness).
>
> What do others think is a reasonable scenario? I'd particularly like to 
> hear from Clay. Clay, I know we're likely to disagree over the meaning of 
> my VSE numbers once I have them ready; and, only human, we'll probably both 
> tend to rationalize to make our points. I think that it will help 
> ameliorate that disagreement if we undercut those future rationalizations 
> by each precommitting to take our own chosen set of numbers seriously, even 
> if those are two separate sets of numbers.
>
> Jameson
>
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